CAD Clinic: Points, Links and Shapes

Subassembly points, links and shapes allow Civil 3D to label their values in a section view.

Civil 3D creates subassemblies from points, links and shapes. The value of subassembly points, links and shapes is that they provide Civil 3D with the ability to label their values in a section view.

Subassembly Points
Subassembly points define the vertices of the subassembly shape and its two connection points. One connection point is towards the assembly, and the other is where the next outside subassembly connects to the current subassembly. The Civil 3D Help documentation identifies these points starting with P1. P1 is the connection point towards the assembly, and it is the first point of the subassembly shape. The outside connection point is usually the top right or left point on the subassembly.

Even though the Help file identifies the points with number prefixed with the letter P (P1, P2, P3?), each point has a specific name and numeric code called a Standard Point Code (figure 1). For example, when looking at the sample basic curb and gutter subassembly, the P1 point has the Standard Point Code of 31 or flange, the P2 point has the Standard Point Code of 32 or flowline gutter, the P4 point has the Standard Point Code of 35 or back curb, etc.

The Standard Point Codes are the most important codes for the subassembly because they represent the names of the feature lines a corridor uses to build a roadway model. Another importance use of these codes is annotation for a section view. Point codes allow Civil 3D to create offset and/or elevation section labels.

Subassembly Links
Between each vertex (Standard Point Code) on the subassembly is a link. A link creates the outside edge of a subassembly shape (figure 1). The L1 link connects points P1 (Standard Point Code 31) and P2 (Standard Point Code 32); the L2 link connects point P2 (Standard Point Code 32) and P3 (Standard Point Code 33), etc.

Subassembly links provide important data to Civil 3D. First, a link is data for annotation. A link provides Civil 3D with a way of annotating a grade or slope value on an assembly.

Second, using the sample basic curb and gutter subassembly as an example, it has three links that define a top (L1, L2 and L3) and the L5 link that defines the datum. These two links provide Civil 3D with data to create surfaces (top and datum). From two surfaces, a user can create a representation of the design (top) or calculate an earthworks cut and fill (datum).

Subassembly Shapes
Taken together the points and the links create a shape, e.g., the shape Pave1 (figure 2). The name of the subassembly is Basic Lane, but it has points, Standard Point Codes, links and a shape name, Basic Lane. The type of annotation Civil 3D creates from a shape is a shape's name. However, the most important value from a shape is an area. This area is the basis for computing quantity take off values.

Figure 2. The definition of Basic Lane's shape.

Annotating with Points, Links and Shapes
The Section View and Section Label styles primarily annotate the existing ground or finished ground not the roadway section. The annotation of an assembly in a corridor section comes not from the Section View or Section Label styles, but from Code Label Styles of the Multipurpose Styles branch of Prospector Settings. The Code Label Styles reference the markers (points), link and shape of a subassembly in an assembly (figure 3).

Figure 3. The Code Label styles reference the markers (points), link and shape of a subassembly.

Marker, link and shape label styles are generic. A marker label style does not look for a specific Standard Point Code; it uses the location of the Standard Point Code to determine the offset and possibly the elevation for the label. The same is true for link and shape label styles; they are generic, and you can apply them to any link or shape in the assembly.

Code Set Style
Rather than identifying a label with a subassembly's points, links or shapes, Civil 3D uses an intermediate step. Civil 3D uses Code Set Style that defines what Standard Point Codes, links and shapes of an assembly display annotation. The name of a code set style is an alias for a list of styles an assembly displays when a style is specified for a point, link or shape. When creating a section view, you assign the code set style to the view.

The Civil 3D content style, All Code Set Style, identifies all of the point, link or shape names from the subassemblies of an assembly. Each point, link and shape in the list has a style that affects how the items show on the screen. The Label Style column specifies if an item displays any annotation in a section view (figures 4, 5 and 6).

Figure 4. Identifying the links of a subassembly.

Figure 5. Identifying the points of a subassembly.

Figure 6. Identifying the shapes in a subassembly.

What is important is not the Code Set Style, but the Code Label Styles (the entries in the Label Style column) associated with the set.

Code Label Style
You should create a code label style that is generic enough to apply to several codes within a subassembly. For example, the Offset/Elevation Style is generic for most point code annotation. However, you can have multiple styles.

A code label style references a point, link or shape. As a result when reviewing or defining each type of style, the component names in the style reflect the element they label. Figure 7 represents a generic offset/elevation style. The style is generic enough that you could label any Standard Point Code.

Figure 7. A generic offset/elevation style.

The style in figure 8 represents a link style. This style focuses on labeling the slope or grade of the element it is assigned to. Changing the format of the label is as simple as changing the format string of the contents entry.

Figure 8. A link style.

Assigning a Code Label Set
The assignment of a code label set occurs as you create a section view (figure 9). The Create View or Create Multiple View commands display the Create Section View dialog box. In the Select sections to draw, area is a style column. This column assigns the label to the various sections in the view. The assignment of the All Codes Code Set Style assigns its code label styles to the section view. If All Codes has only two point codes with styles, the resulting section labels only those codes. If you add codes to the style after creating a section view, the section view updates to show the new annotation entries added to the Code Set Style (figure 10).

Figure 9. Creating a section view.

Figure 10. The updated section view.

About the Author: Phillip Zimmerman

In her easy-to-follow, friendly style, long-time Cadalyst contributing editor and Autodesk Technical Evangelist Lynn Allen guides you through a new feature or time-saving trick in every episode of her popular AutoCAD video tips. Subscribe to the free Cadalyst Video Picks newsletter and we'll notify you every time a new video tip is published. All exclusively from Cadalyst!